<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
	.container{
    background-color: silver;
    width:100%;
    position:relative;
    display: inline-block;
}
.dummy{
    margin-top: 100%;
}
.content{
    position:absolute;
    left:0;
    right:0;
    top:0;
    bottom: 0;
}
	</style>
</head>
<body>
	
<div class='container'>
    <div class='dummy'></div>
    <div class='content'>content</div>
</div>
</body>
</html>